Dental calculus is an ash gray, yellowish or dark brown calcified substance depositing on dental crowns, exposed dental root surfaces, or surfaces of restorative dental materials. Plaque (dental plaque) adheres to surfaces of human teeth. In the plaque, a reaction occurs by which inorganic salts become more adhesive, and calcification starts from a layer which touches a tooth surface. The calcification advances as the plaque becomes older and thicker, and new plaques adhere to the surface of the calcified plaques and causes calcification. Dental calculus is formed by repetition of this process.
Seventy to eighty percents of components of supragingival dental calculus consist of inorganic salts, and most of them consist of hydroxyapatite (Ca10(PO4)6(OH)2). Calcium phosphate, calcium carbonate, magnesium phosphate and the like may sometimes be also contained. Further, dibasic calcium phosphate and tribasic calcium phosphate may sometimes be contained. Organic components contained in dental calculus are bacterial cells, and they include cell walls of gram positive bacteria and endotoxins as outer membrane components of gram negative bacteria. Dental plaque formation more easily progresses on dental calculus surfaces than on smooth tooth surfaces, and dental plaque adhering to dental calculus stimulates periodontal soft tissues to become etiologic substance. Accordingly, scaling of teeth is important as one of the fundamental treatments in prophylaxis and therapy of periodontal diseases.
For removal of dental calculus, methods involving mechanical removal of calculus by using a scaler or the like have been conventionally applied. However, the methods have problems in that the treatment takes a long period of time due to hardness of dental calculus, and thus patients, dentists, or dental hygienists bear burdens. As a means for chemically dissolving and removing dental calculus, for example, an agent for dissolving dental calculus described in Japanese Patent Publication (KOKOKU) No. 7-53653 is known. However, the dissolution action of the agent is totally insufficient from a practical view, and due to irritancy by chemicals on periodontal soft tissues, the agent has not been used in the field of clinical dentistry. Under the circumstances, it is desired to develop an agent for dissolving dental calculus that can dissolve dental calculus in a short period of time and dose not irritate or damage tissues in oral cavity such as periodontal soft tissues or dental tissues. It has been reported that phytic acid is effective for suppressing dental plaque formation (Nordbo H., et al., J. Dent. Res., 51, 800, 1972). However, this reference neither suggests nor teaches that phytic acid has an action of dissolving dental calculus.
When a dental caries is formed, a therapy generally applied involves cutting and shaving off the caries by using a rotary cutting instrument. However, the therapy has a problem in that a patient is scared by vibration and sound of the instrument, generation of pain and the like during the treatment. When a dental caries is soft, the caries may be scraped by using a dental instrument called an excavator. However, it is difficult to completely scrape a dental caries. Recently, a method has been used which includes dissolving dental caries by using an agent for dissolving dental caries developed in Sweden and then scraping off the caries by using a unique instrument (trade name: Carisolv, produced by Medi Team, Japanese Patent No. 2728306). However, this method has a problem in that softening effect of Carisolv is weak and thus the treatment takes a long period of time. Furthermore, the method also has drawbacks in that the treatment requires a mixing step before use, which is a complicated operation, and that the agent has poor storage stability and the like. For these reasons, it is desired to provide an agent for dissolving dental caries that can easily dissolve and soften dental caries and has superior storage stability, and achieves a treatment with convenient operations.